Cast ceramic anode for metal oxide electrolytic reduction
The invention is a method for producing a cast ceramic anode for metal oxide electrolytic reduction by feeding metallic iron and metallic nickel in solid form to an oxidizing reactor; melting and oxidizing the iron and nickel and forming molten nickel ferrite; mixing the molten nickel ferrite with dopant in a holding vessel such as ladle or tundish to increase electrical conductivity of the mixture, and casting the mixture into a mold to form a near net shape of the desired anode. Apparatus for carrying out the method, and the resulting product are also disclosed.
1. A method for producing a cast ceramic anode for metal oxide electrolytic reduction, comprising the steps of:
feeding metallic iron and metallic nickel in solid form to an oxidizing reactor;
melting and oxidizing the iron and nickel and forming molten nickel ferrite;
discharging molten nickel ferrite from the oxidizing reactor at a temperature sufficient to maintain the molten nickel ferrite in the molten state;
adding a dopant to the nickel ferrite and forming a mixture; and
casting the mixture into a mold to form a near net shape of the anode.
2. A method according to claim 1 further comprising attaching an electrical connector to said anode.
3. A method according to claim 1 wherein the metallic iron and metallic nickel are fed in briquet form to the oxidizing reactor.
4. A method according to claim 1 wherein the dopant is selected from the group consisting of zinc, cobalt, or lithium compounds.
5. A method according to claim 4 wherein the compounds are oxides.
6. A method according to claim 4 wherein the compounds are carbonates or sulfides.
7. A method according to claim 1 , further comprising stirring molten material in said ladle or tundish with oxygen-containing gas to also oxidize any remaining metal.
8. A method according to claim 1 , further comprising a post-casting heat treatment of the cast anode in an oxygen-containing atmosphere.
9. A method according to claim 8 wherein said post-casting heat treatment is an anneal of the cast anode.
10. A method according to claim 8 wherein said post-casting heat treatment is a phase composition adjustment comprising: soaking the cast anode at a temperature of from 1200° C. to 1400° C. for a sufficient time to oxidize any remaining metallic nickel and metallic iron.
11. A method according to claim 10 further comprising slow cooling the cast anode to a temperature below 1200° C.
12. A method according to claim 11 further comprising soaking said anode in an oxygen-containing gas for a second period of time at a temperature below 1200° C. for final phase composition adjustment and microstructure adjustment.
13. A method according to claim 11 further comprising hot isostatic pressing of the cast anode at a temperature of at least 1000° C. and a pressure of at least 1360 bar for a period of from about 4 to about 8 hours.
14. A method for producing a cast ceramic anode for metal oxide electrolytic reduction, comprising the steps of:
feeding at least one compound selected from the group consisting of nickel oxides, iron oxides, nickel ferrite, iron sulfides, nickel sulfides, iron carbonates, nickel carbonates, or mixtures thereof, to the melting vessel;
melting the compounds and forming molten nickel ferrite;
discharging molten nickel ferrite from the melting vessel at a temperature sufficient to maintain the molten nickel ferrite in the molten state;
adding a dopant to the nickel ferrite to form a mixture; and
casting the mixture into a mold to form a near net shape of the anode.